Project Summary Transplant chronic rejection accounts for 30% of patient deaths following cardiac transplantation. The hallmark lesion of solid-organ allograft chronic rejection (CR) is transplant vascular sclerosis (TVS). TVS is accelerated by inflammation and immune response at graft sites. Many factors influence the inflammatory immune environment near a graft to promote chronic rejection. One such factor of particular interest is infection with Human Cytomegalovirus (HCMV). Because approximately 75% of the human transplant donor/recipient population is positive for HCMV, the development of novel therapies that mitigate HCMV effects is critical to treat transplant recipients receiving HCMV+ donor organs to increase graft survival and prevent CR. However, the viral mechanisms associated with HCMV-acceleration of allograft TVS and CR are poorly understood. A better understanding of these mechanisms is critical to improving survival and quality of life for transplant patients. Current literature suggests that enhancement of the immune response both against the virus and the graft are leading candidates for early graft destruction and promote viral-acceleration of allograft disease. Host chemokines promote graft rejection by recruiting and activating immune cells, thereby suggesting that virally encoded chemokines may also play a role in promoting graft rejection. HCMV is known to modulate the chemokine axis by inducing chemokine expression following infection, and to encode multiple chemokines and chemokine receptors, including the chemokines UL128 and UL130. However, the role that these chemokines play in viral pathogenesis and acceleration of transplant rejection remains poorly understood, and is the focus of our research. We will investigate these relationships using in vitro assays mimicking a rat cardiac transplant model with RCMV infection and in vivo studies for cellular infiltrate to cardiac tissue prior to transplantation, utilizing the RCMV homologue of HCMV UL130, RCMV R131. In particular, we hypothesize that the virally- encoded CC-chemokine R131 promotes immune cell migration and increases immune cell infiltrate prior to transplantation, which may lead to inflammation and acceleration of TVS following transplantation in an in vivo rat cardiac transplantation model. Our second hypothesis is that R131 has a similar role as UL130 in PEC- mediated entry into macrophages and endothelial cells, which may foster widespread viral dissemination in the allograft, enhancing graft disease. We will address these hypotheses in Specific Aim 1 by defining post- translational modifications to R131 and by identifying motifs present within RCMV R131 that mediate migration in vitro and in vivo. Our goal is to generate a panel of viral mutants that lack chemotactic activity. In Specific Aim 2, we will define the role of R131 in entry into macrophages and endothelial cells and the impacts of R131 mutations in pathogenesis in vivo. In Specific Aim 3, we will determine the degree to which mutations in R131 may affect survival of and pathology in cardiac allografts.